The use of polyolefin pipe has become commonplace for utilities. Other industrial uses of polyolefin pipe have increased with the development of fusible polyolefin materials. Fusible materials such as polyethylene and polyethylene alloys are being substituted for steel, ductile iron, clay, concrete, and bell and spigot PVC pipe for industrial uses in which high pressure and heat are not a concern. These polyolefin materials are typically lighter in weight and almost completely unaffected by corrosion. For example, polyolefin pipe is being used to transport corrosive chemicals, waste water, potable water, storm water, and for irrigation systems, leachate systems and petrochemical collection systems.
A number of circumstances will require fusing two pieces of polyolefin pipe together. The process of fusing polyolefin pipe consists of placing two matching surfaces on either side of a heat source, heating the surfaces to a predetermined temperature, removing the heat source, and forcing the two surfaces together under pressure.
Many factors affect the fusing of two pieces of polyolefin pipe. Polyolefin pipe is manufactured in many different wall thicknesses and diameters. In addition, fuses of the two pipes may be performed in a wide range of environments, from shops with controlled conditions to open pits subject to ground and weather conditions. An effective fusing apparatus would have to adapt to all such conditions. Further, depending on the result desired, the two pieces of pipe may be fused end to end (butt fusing) or with the end of one joined to the sidewall of the host pipe (sidewall fusing). Butt fusing is generally easier to accomplish. Sidewall fusing is accomplished by either of two methods: (1) fusing a fabricated saddle with a pipe nipple already attached onto the sidewall of the host pipe; or (2) fusing onto the host pipe a pipe with a concave radius on one end matching the convex radius of the host pipe.
Prior art devices accomplishing sidewall fusing are described in U.S. Pat. Nos. 3,998,682, 4,533,424, 4,542,892, and 5,613,807. Fusing machines currently being used employ manually-operated screws, hand-pumped hydraulics, auxiliary-powered, high pressure hydraulics, or a combination of these in order to provide the movements and pressures necessary to complete a sidewall fusion. Machines employing manually-operated screws or hand-pumped hydraulics are slow, preventing an operator from joining the heated surfaces together quickly after the heat source is removed. Auxiliary-powered, high-pressure hydraulic machines must have valves, hoses, and cylinders capable of operating at high pressures, making the machines heavy and expensive; additionally, replacement power units for such machines are not readily available at rental outlets and contractor supply houses.
U.S. Pat. No. 5,013,376 discloses and claims a method of heat fusing which uses hydraulics and is controlled by a programmable computer. The patent states generally that the apparatus can be used for sidewall fusing; however, the apparatus described would be unable to perform sidewall fusions. For instance, the apparatus has no way of moving and attaching sidewall pipe (all movements described are along a longitudinal axis). No provision is made for fusing two different sizes of pipe, which would call for different soak times. Sidewall fusing requires a special heating plate with concave and convex faces. Also, the apparatus described uses a facing tool (useless in sidewall fusing) but has no provision for making radius cuts.